The Montana Constitutional Convention of 1889 was a meeting of delegates from the U.S. Territory of Montana from July 4 through August 17, 1889, in Helena, Montana, the territorial capital. The delegates created what would become the basis for legal government in the State of Montana, or Montana's original constitution.

In April 1866, not even two years after the Territory was established, delegates met in the bustling mining camp of Helena to charter a state constitution in hopes of attaining a rapid route to statehood. Largely a scheme of Secretary of the Territory, and acting territorial governor at the time, Thomas Francis Meagher, this attempt at statehood would abruptly fail due to a lack of adequate population and a hostile political environment in Washington D.C.^[1] The document produced at this meeting has been lost to history. The next attempt at statehood occurred much later in a very different Montana Territory. By the 1880s, a railroad line and large scale mining had transformed the Montana economy and its population.

75 delegates elected in May

• Montana Constitution of 1889, as passed on August 17, 1889
• Proceedings of the Montana Constitutional Convention of 1889
• Index to Proceedings and Debates of Montana Constitutional Convention of 1889
• Guide to Montana Constitutional Convention (1889) records at the Montana Historical Society Research Center
• Guide to Constitutional Convention Materials at the Montana Historical Society Research Center